The typical automotive vehicle comprises an accelerator pedal for operating the vehicle's powerplant. Historically, mechanical linkages have been used to couple the pedal with a device that regulates the amount of fuel that is introduced into the engine. With the advent of electronics in controlling engines, coupling of an accelerator pedal with an engine can involve the use of an accelerator pedal sensor that converts a pedal position input into an electrical output that is delivered to an electronic control module (ECM) that in turn controls the engine.
One type of accelerator pedal sensor comprises a potentiometer whose tap is coupled with an accelerator pedal input such that the potentiometer output is correlated with the pedal input. Additionally, this accelerator pedal sensor comprises an idle validation switch that switches at a position proximate closed throttle position for the purpose of distinguishing between idle and non-idle. The position at which the idle validation switch switches is correlated with the position of the potentiometer tap, and when tolerances are taken into account, this position will, in an acceptable pedal sensor, lie within a range of acceptable positions proximate closed throttle. If the actual switching point lies outside of this range of acceptable positions, the sensor is deemed to be out of calibration, and hence unacceptable.
When a number of vehicles each having such an accelerator pedal sensor were placed in service, actual experience showed that testing of the accelerator pedal sensor was often performed as part of diagnostic procedures for those vehicles. The manufacturer's published test procedure for the sensor comprises a number of steps that are documented by eleven pages in a service manual. For whatever reason, actual experience has also shown that many of the accelerator pedal sensors that are deemed out of calibration by servicing personnel in the field, are actually found not to be out of calibration when returned to the manufacturer.
It is believed that a better testing procedure can significantly reduce the number of allegedly out-of-calibration sensors that are returned to the manufacturer and subsequently found not to be out of calibration. It is to an improved sensor testing procedure for achieving such reduction that the present invention is directed. By utilizing the improved procedure of the invention, it is believed that field servicing personnel will be better able to distinguish an out-of-calibration sensor from a properly calibrated one so that it will become less likely either that a properly calibrated sensor will be returned to the manufacturer under an erroneous warranty claim or that a customer will have to pay for replacement of a sensor that does not need to be replaced. Because it will eliminate many erroneous diagnoses, the method of the invention is expected to improve field servicing, and in turn, customer satisfaction.
The present invention provides several significant advantages over the prior procedure that spans eleven pages of a service manual: it can be performed more easily, more quickly, and more accurately. The economy in time and the improvement in accuracy should yield meaningful savings to the customer, the servicer, and the manufacturer, and lead to better relations among all concerned.
In a presently preferred embodiment of the inventive method, the only special equipment needed to perform a test comprises a special jumper, a special instruction and data entry sheet, and a special slide calculator. The special jumper is inserted between existing wiring connectors in a vehicle to enable the sensor to be tested without removing it from the vehicle. The special jumper comprises an interface box containing two LED indicators that are observed by servicing personnel during a test. The interface box also comprises test points to which servicing personnel can connect their own voltmeter to measure certain voltages during a test. The special instruction and data entry sheet provides an organized format for entry of certain data obtained during a test. This data is used in reaching a determination as to whether a sensor is in or out of calibration, and the sheet itself serves as a written record of the test data. The special slide calculator contains instructions for its own use and serves to enable certain test data be quickly converted into data against which other test data is compared in reaching the determination. A final piece of equipment that is used during a test is a voltmeter, preferably a digital one, which is typically a piece of standard service equipment belonging to servicing personnel.
A detailed description of the invention will now be given with reference to the accompanying drawings that show a presently preferred embodiment according to the best mode contemplated at this time for carrying out the invention.